For maintenance and control purposes, the spinning rotors of an open-end spinning machine must be easy to access and monitor. If a spinning rotor of a spinning device, which customarily is embodied as a spinning station, is to be checked, removed or exchanged, a cover of the spinning device, e.g., a cover to a spinning housing in a typical open-end spinning station, is opened until into an upwardly pivoted position. This type of service check is performed, for example, if it is suspected that a spinning error or a malfunction has been caused by the spinning rotor, or if the yarn-piecing operation is repeated too often, or too may undesired cleaning cuts of the spun yarn are performed over a given period of time.
After the spinning box has been opened, the spinning rotor is accessible. However, prior to touching the rotor cup which, in the view of the operator, is located at the front of the opened housing, the operator must absolutely assure himself that the rotor has actually come to a stop. A clear visual indication that the rotor is at a standstill is provided by a marking applied to the rotor cup which does not move when the spinning rotor is stopped. The mere presence of such a marking on spinning rotors running at high revolutions is invisible to the eye. If no stopped marking is visible, the rotor cup may still be rotating, but it is also possible that the rotor is stopped but it has no markings. To make sure that a running spinning rotor is not touched, the operator typically takes more time to visually observe the rotor. This situation leads either to undesired waiting times or to safety risks.
If it has been found that such markings are not provided, an operator often applies these himself, for example in the form of a line applied by a felt-tip pen to the rotor cup. However, markings applied in this way must soon be redrawn, since they fade or can be rubbed off by the cleaning head of a traveling yarn piecing cart. Regardless, such markings in the form of a line are unsuitable as a basis for assuring a clear indication whether the correct types of spinning rotors have been employed in the spinning device. To perform such a check, it is therefore customarily necessary to remove the entire spinning rotor from the spinning device, so that the class of rotor can then be visually determined. If the spinning rotor is the correct type for the current spinning operation, the spinning rotor is reinstalled after checking. This method is awkward and time-consuming.
Not previously published German Patent Document DE 197 55 060, describes the basic type of spinning rotor discussed above. This document discloses a spinning rotor whose identification mark is in the form of either a bar code arranged in the area of the rotor cup or an electronic information carrier, for example in the form of a transponder. This marking is detected by means of a sensor arrangement, which prevents operation with unsuitable spinning rotors. During operation, these markings can also be used for measuring the number of revolutions by means of the sensor arrangement. However, such markings are still unsuitable for a visual check of the rotor type, since the operator cannot visually read bar codes or transponders to determine a sufficient indication as to the type or class of rotor. For spinning rotors with bar codes or transponders it is still necessary for the operator to remove the rotor to make such determination visually.